Rigify rig bone selection problem
I had the same problem -- digging around the blender bug tracker I found this ticket: https://developer.blender.org/T47940 which describes the problem.
I was also using open source gpu drivers.

This is fixed (at least for me) on the latest builds; not yet on the official version (2.77a).
If you still have the problem, try a newer version from here,
https://builder.blender.org/download/